Details
The differences in the inertial sleeve of Magnum vs. Standard has extra mass/inertia included with the magnum sleeve to ensure operation of the mechanism with the use of one (rather than two, as in 2-3/4" std. barrels) gas hole in the barrel cylinder.
Extra mass keeps the action bar assembly in motion when shot, since only one gas hole pushes the piston assembly and therefore needs a bit more inertia to reliably complete the cycle (even though using higher pressure gas).
Therefore, for light loads, (if failing to complete the bolt cycle i.e. underpowered) changing to a lighter inertia sleeve (std. 2-3/4") is going in the opposite direction. (Have you seen the very light sleeve used on the Supermag 11/87? Gas bleed system reduced the inertial need to some extent)
I do not believe that the heavier sleeve will have enough extra inertia to make it's use shooting heavy loads to create much more possibility of damage vs. what is considered as normal cyclic pounding.
You cannot have it both ways, where the heavier sleeve is posited as possibly causing damage, and yet not keep parts moving when functioning with lighter loads. Shooting of very heavy loads would be the biggest reason to re-install the MAGNUM barrel, correct?
Another point to consider is that the standard 2-3/4" gun was considered as able to work and withstand everything up to the heaviest 2-3/4" turkey loads (now 1-5/8 oz. Winchester @ 1250 fps, I believe), so the battering from just about any combination is less than most have been led to believe.
You should keep track of bolt buffer condition as well as note the condition of the slide lock buffer (plastic piece at rear of action bar) to monitor protective/sacrificial parts condition.
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This posting from 2-1/2 years ago covers similar details with extended explanations.
http://www.thehighroad.org/showthread.php?t=245911&highlight=1100
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